The Core project provides a central resource for the Program. It encompasses four Subcore Units, which perform the following specific operations: (1) Image Acquisition and Analysis; (2) Statistical Analysis, Data Storage, and Computer Facilities; (3) Subject Recruitment and Induction; and (4) Monitoring of Data Quality and Research Progress. All of these operations, which are essential for the execution of all studies involving humans, are continuous over time. This team of investigators has an established record of carrying out such activities in other research protocols, for more than a decade.